Method of producing metallurgical coke



May 3, 1960 c. JULLY 2,935,450

METHOD 0F PRODUCING METALLURGICAL COKE Filed July 16. 1956 L Y Wea/fb'sok/'ng coa/ I C4 4 Coarse rams (QJ to2/7 2r mga ,n )1060252017101izan/h and: ra/h pura/h CoarJe rana/es Orr 2,935,450 METHOD orrnontgnxsg METALLURGICAL Charles Jully, Carling, France, assignor toHouilleres du Bassin de Lorraine, Merlebach, France Application July 16,1956, Serial No. 597,884 10 Claims. (Cl. 202-33) This application is acontinuation-impart of application Serial No. 222,530, tiled April 23,1951 (now abandoned), entitled: Method of Producing Metallurgical Coke.

Weakly coking coals of low bitumen content from the Lorraine Basin inFrance called gras A, gras B and liambants gras pertaining to the highvolatile bituminous coal category and high-volatile bituminous coals ofinferior categories, and similar coals have hitherto been considered asunsuitable for producing metallurgical coke in'spite of theirfusibility. 'As a matter of fact, cokes obtained by carbonizing thesecoals without a special preliminary treatment do not offer a sufficientresistance to crushing.

. For the sake of clearness in the present specification and-as thegroups of coals concerned are classified in subgroups it is deemednecessary to indicate the conditions in which -the indices definingthese sub-groups are found. The amount of volatile materials isdetermined in accordance with the French Standards AFNOR No. 03-004.This is based on a test carried out in a crucible of enamelled porcelaineither of the so-called Bayeux variety or of dull platinum. Thiscrucible has a top diameter substantially equal to the height and abottom diameter substantially equal to one-half of the height, thelatter and the topdiameter ranging from 30 to 45 mm.

` AFor heating the Crucible an oven adapted to maintain therein aconstant temperature of 960 C.il0 C. is used. v The crucible should beheated with a progressively increasing temperature having asubstantially linear characteristic of about 100 C. per minute, thefinal temperature measured inside the crucible and at the contact of itslower face being iixed at 960 C. and reached after a heating periodranging from 9 to l1 minutes. This nal temperature is maintained forminutes. A suflicently reducing atmosphere should be kept around thecrucible in ord'erto prevent the sample from burning during the test.

The test is carried out by heating the crucible to full red and allowingit to slowly cool down with its cover in a dryer. After measuring theweights of the crucible and cover assembly a test sample weighing l gramis taken from the mass of the coal to be tested and this sample isspread to a uniform layer on the bottom surface of the crucible. Thissample is then wetted with 30 drops of a liquid containing 50% of waterand 50% of pure alcohol, these drops being uniformly distributed' verthe entire surface. Then the crucible fitted with its top.is introducedinto the heating device and the heating step is carried out in areducing atmosphere as set forth above. The erucible is finally takenfrom the oven and allowed to cool in the dryer, and after removing anytrace of dust which might possibly adhere to the external walls thecrucible is'weighed within 60 minutes at the latest.

'The' swelling index is found according to the French standard methodAFNOR No. 11-001 which is similar to the British method B.S.S. 1016-1942and also to the American method A.S.T.M. D720-46.

' Resistance to abrasion and to splitting is conveniently j I'2,935,456Patented May 3, 196,0y

determined by means of the Micum drum test (Mission Inter-Allie deContrle des Usines et des Mines) adopted in -France and Belgium since1924 for the testing of Rhur cokes. It is performed by means of a hollowdrum with a smooth inner surface constructed of sheet steel of athickness of 5 mm., and closed at both ends and mounted with its axishorizontal. It is 1 metre in diameter and 1 metre long and has securedto the inside surface at regular intervals four angle irons extendingparallel to the axis and projecting radially 100 mm. from the surface.Introduction into the drum of the coke to be tested is eifected by wayof a curved hinged door 500 x 600 mm. provided with securing means. Bymeans of an electric motor operating through reduction gearing thecylinder is rotated at a speed of 25 revolutions a minute about its axisin the direction of the unencumbered sides of the angle irons.

The operator is provided with three sheet metal sieves 4 or 5 mm. thickand 700 X 500 mm. in size, perforated respectively with circular holesof 50 mm., 40 mm. and l0 mm. Each sieve is arranged in a wooden hopper20 cm. high. There is also a wooden box for receiving the crushed cokeof the same size as the hopper for the sleves. The method of operationis as follows: The sample of 50 kgs. of coke of a size greater than 50mm. is introduced by hand into the drum and the door is ythen secured.The drum is then subjected for 4 minutes to rotation at a speed of 25revolutions a minute i.e. 100 revolutions per test. After the apparatushas come to rest the door is opened and the complete contents of thedrum including dust are extracted. These contents are passed two orthree times through `the sieve with 40 mm. holes then through the sievewith 10 mm. holes. The fractions of coke of a Size greater than 40 mm.and of a size less than l0 mm. are weighed separately. F our testsarekmade successively on four distinct samples each of 50 gs.

In order to express the results, calculation is made for each test ofthe percentages of coke greater than 40 mm. and less than l0 mm. Thearithmetic mean of the results obtained with the four samples representsthe iinal result on which the quality of the coke examined can bejudged.

The percentage of coke from 0-10 mm. in size called the Micum index M10or tumbler non-stability on l0 mm. screen, characterises the resistanceto abrasion and indicates the proportion of the coke which is capable toact as a disturbing element for the working of the blast-furnaces, moreparticularly by its binding with their lining. The percentage of coke ofa size greater than 40 mm. called the Micum index M40'or tumblerstability on 40 mm. screen characterises the resistance to crushing andsplitting.

A good metallurgical coke should have an index M40 substantially equalto, or higher than, 80 and an index M10 at the most equal to 8.

As already stated the groups of coals concerned are divided intosubgroups according to their characteristics:

(i) Coals of the type gras A in Lorraine and approximately of the noncoking high Volatile A bituminous coal category, having a percentage ofVolatile matter ranging from 27% to 36% (calculated on pure and drycoal), a swelling index ranging from 6 to 9, an oxygen content comprisedbetween 6% and 8% and Micum indexes M40 between 35 and 40 and M10between 6 and 8.

(ii) Coals of the type called gras B in Lorraine and approximately ofthe non coking high volatile B bituminous/coal category, having from 35%to 42% of volatile matter, a swelling index ranging from 4 to 7, apercentage of oxygen ranging from 8% to 10% and Micum indexes M40between 25 and 35 and M10 between 6 and 8.

(iii) Coals of the type ca'lled ambants gras in Lorraine andapproximatelyof the non coking high volatile B bituminous coal of lowergrades and high volatile C bituminous coal categories, both of whichhave from 36% to 45% of volatile matter, a swelling index .of 2 to' 5,from 9.5% to 12.5% of oxygen and Micum indexes M40 between and 30, andM10 between 6 and 8.

Of course, the above figures are given solely as rough limits and thisinvention is chiefly concerned with coals of sub-groups called gras Band particularly with coals of sub-group called ambants gras ashereinabove defined.

The high volatile matter and oxygen contents of said coal sub-categoriesshow that they relate to coal pertaining to supplies of recent formationwhich as well known necessitate a quick heating law, i.e. a hightemperature, in order to attain a certain degree of fusion.

Further the high volatile matter content and the small Micum indexes M40of said coal sub-categories indicate that said coals when carbonized aresubjected to a notable shrinkage causing important cracks, The practiceshows moreover that their bitumen content is very low and that saidbitumen is not thermostable. Therefore when said coals are carbonizedfor manufacturing coke the total loss in fluidity of their bitumen isattained before their volatile matters have wholly escaped so that whensaid bitumen solidifies the mass of coke cracks under the action of thedriving off of the gases which have not escaped from said mass when saidbitumen was uent.

The main object of the present invention is to provide a process forremedying the lack of thermostable biturnen of said coals in order tomanufacture from said coals a metallurgical coke having Micum indexesM40 substantially equal to, or higher than, 80 and M10 lower than 8,i.e. a coke complying with all the requirements of the metallurgy ofiron.

For this purpose, the small coal of said sub-categories of coal issubmitted to a dedusting operation for freeing it from free fusain by amechanical preparatory treatment which may consist in pneumatically orhydraulically removing mud and dust from the coal. Afterwards by acrushing operation followed by a size-grading screening said dedustedsmall-coal is freed from almost the whole fusain remaining therein. Thena ternary mixture is prepared, vsaid mixture having a percentage ofvolatile matter ranging from 27% to 33%, preferably from 29% to 30%, andcomprising as main component from 65% to 75% by weight of saidsmall-coal practicallyfreed from fusain, and as secondary componentsfrom 9% to 28% by Weight of additional coking bituminous coal having avolatile matter content of 18% to an oxygen content less than 5% andMicum indexes M40 higher than 80 and M10 lower than 8, and from 7% to16% by weight of small grains of a carbonaceous material havingpractically no volatile matter. Said mixture is subjected to acompression step in order to attain a bulk density ranging from 1,000kg./m.3 to 1,100 kg./m.3; then it is carbonized at a temperaturecomprised between 1,150 C. and 1,350" C. according to thecharacteristics of its components.

The use of the aforesaid coking bituminous coal as an additional coalhas :for its object, on the one hand, to supply to the mixture thethermostable bitumen lacking in the basic coal and, on the other hand,to decrease the volatile matter content of said mixture with respect tothat of said basic coal.

The utilization of a carbonaceous material having practically novolatile matter as a secondary component for the mixture decreases thevolatile matter content of said mixture with respect to that of thebasic coal and adds to said basic coal an indifferent material having,as a consequence of its process -of manufacture, a state of sur- 4 facewhich necessitates the minimum quantity of bitumen to be coated thereby.

The percentages of the three components of said ternary mixture are sochosen in accordance with the actual characteristics of the basic andadditional coals that the volatile matter content indicated for saidmixture is obtained while taking into account the thermostable biturnencontent which warrants good melting conditions. If the volatile mattercontent is increased, during the carbonization a great shrinkage takesplace which, while less than that occurring during the carbonization ofthe basic coal alone, is sufhciently important for causing notablecracks Afor the thus manufactured coke. If on the contrary said contentis decreased the mixture behaves as a lean coal, such as anthracite forexample, does not melt and gives a pulverulent coke. In both cases thecoke which is thus manufactured is useless for metallurgical purposes.

'Die compression step to which the ternary mixture is subjected has forits object to bring the grains of the basic coal nearer to each other upto an interpenetration thereof so ,that the leaking of the bitumen influid state between said grains during the carbonization stepalreadyensures their mutual binding. It is to be noted that the conventionalbulk density for a coke oven charge ranges from 700 to 750 kg./m.3.

The earbonization temperatures are determined by the nature of the basiccoal, which, as hereinabove indicated, is extracted from coal suppliesof recent formation and ltherefore necessitates a quick heating law inorder to attain a certain degree of fusion. If the carbonizationtemperature decreases the manufactured coke is a badly melted cokehaving a Micum index M10 substantially higher than 8, i.e. a coke whichis friable and of inferior quality for metallurgical purposes.

The following description relating to a specific manner in which themethod of this invention may be carried out is given solely by way ofexample and should not be construed as limiting the scope of theinvention as set forth in the claims attached thereto.

The accompanying drawing showing a ow sheet discloses the steps of saidmethod.

After the weakly coking coal defined hereinabove has been treated insome known dry or hydraulic way in order to remove the gangue and thefree fusain therefrom, it is freed from any particles below a certainsize C1 to be determined according to the fusain content of the coalsused, this size being however as small as possible in order to eliminateonly detrimental excess coal. With the conventional washing equipmentsand when small coals are used, a size of about 1 mm. is generallysuitable. Said particles or small coal as well known consist in fusain.

Then any coal grains above a certain size CB selected between the limitsizesof 10 mm. and. 20 mm. are separated from the coal mass. Thesecoarse grains consisting in durain are roughly crushed to a size belowCs and added again to the portion of middle-sized grains comprisedbetween sizes Ci and Cs which consists in vitrain. The aggregate productcomprised between these last sizes is then divided into two fractionsthrough an intermediate cut Cm ranging from 3 to 4 mm.

No further sizing is required for the fraction of middlesized granulescomprised between sizes C1 and Cm, but the other fraction of coarsegranules is crushed to a size smaller than 2 mm. and then added to thefirst fraction.

As a result of these various steps a product is obtained wherein allgranules have a size below Cm without causing the necessary crushingoperations to reduce the smaller granules to powder.

The thus obtained product is characterised in that it containspractically no fusain. Said last component of the basic coal iseliminated with a view to obtain a mixture which is free from aconstituent having a substantial volatile matter content andnecessitatng a substantial amount of bitumen for complete incorporationin said mixture, said constituent being `a non-fusible indifferentmaterial having a structure with a very great and irregusurface foragivenvolume, such as the structure of charcoal.

This product` is the irst component of the ternary mixture to becarbonized.

The second component is coking bituminous coal, for example coalfromtthe Pas-de-Calais, Ruhr or even Saar- Lorrainese. Basins, ofv a sizesmallerV than 4 mm. and preferably 3 mm. V Thiscoal contains r18% to 25%of volatile matter, preferably. 19%.to 21%, an oxygen content lower than5% and-Micum indexes M40 higher than 80 and M10 lower than 8. 1;

The third component of the mixture is granular coke breeze oranthracitic coal culm of a size not above 1 mm. and comprising at least70% of granules smaller than 0.2 mm. The more this third component iscrushed, the better the results obtained, more particularly if granuleshave a surface as smooth as possible.

'I'he ratios in which the above-stated components are admixed may varyto a certain extent provided the amount of volatile matter in themixture is kept within the above By way of example, the followingformulae may be resorted to, the various percentages being establishedin weight:

Formula I Percent Coal of the type called gras B in Lorraine andapproximately of the non cokable'highvolatile B bituminous coal category75 Coking bituminous coal (as from Drocourt in the Pasde-Calaisdistrict) 9 Crushed coke breeze 16 Formula II Coal of the type calledgras B in Lorraine and approximately of the non cokable high volatile Bbituminous coal category 48 Coal of the type called tiambants gras. inLorraine and approximately of the non cokable high volatile B bituminouscoal of inferior categories or high volatile VC bituminous coal category24 Small coal from coking bituminous coal (-as from the Pas-de-Calaisdistrict) 16 Crushed coke breeze 12 Formula III Coal of the type callediiambants gras in Lorraine and approximately of the non cokable highvolatile B bituminous coal of inferior categories or high volatile Cbituminous coal 65 Small coal from coking bituminous coal (as from thePas-de-Calais district) 28 Crushed coke breeze 7 The mixture, afterbeing homogenized by conventional means, is then introduced into arammer charger in which it is transformed by compression into a cakeweighing several tons which is then charged into the coke oven.

The heating temperature, ranging from l,l50 C. to

1,350 C., is rated according to the proportions of the ternary mixtureas indicated in the above formulae. Thus, the temperature is from 1,150to 1,250 C. for Formula I, 1,250 to 1,300 C. for Formula II, and 1,275to 1,350 C. (preferably 1,300 C.) for Formula III. It is of particularimportance that a suitable temperature be observed in the case ofFormula III or any similar formulae.

It will be readily understood that alterations m-ay be brought to theprocess described hereinabove by way of example, without departing fromthe spirit and scope of the invention. Thus, in particular, the oven maybe charged directly without subjecting the ternary mixture to apreliminary compression operation; although not so satisfactory, anappreciable result may be obtained in this case, providedlthepercentage'of additional bituminous coal is increased or, for instance,doubled.

' What I claim'is:

1. A method of producing metallurgical coke having Micum indexes M40substantially equal to 80 and M10 lower than ,8, from'weakly cokingcoals, which coals have moreover a low bitumen content, a highpercentage of volatile matter ranging from 27% to 45%, a swelling indexaccording to theASTM D720-46 method of from 2l to 9 and a h igh oxygencontent ranging` from 6 to 12.5%,'such `as Saar-Lorraine coals of thetypes consisting of gras A, gras B and ,ambants gras, which comprisesfreeing from dust a portion of said weakly coking coal, crushing saiddust-freed portion, separating from the crushed coal small coalcontaining fusain and gangue, crushing the remaining part of the crushedcoal into small grains, preparing a ternary mixture having a percentageof volatile matter ranging from 27% to 33% and comprising as maincomponent from 65% to 75% by weight of the thus obtained small grainsand as secondary components from 9% to 28% by weight of additionalcoking bituminous coal having a volatile matter content of 18% to 25%,an oxygen content less than 5% and Micum indexes M40 higher than 80 andM10 lower than 8, and from 7% to 16% by weight of small grains of acarbonaceous material substantially free from volatile matter,mechanically increasing the bulk density of said ternary mixture, andcarbonizing said ternary mixture with increased bulk density at atemperature between about 1150 C. and 1350 C.

2. A method of producing metallurgical coke, having Micum indexes M40substantially equal to 80 and M10 lower than 8, from weakly coking coalswhich coals have moreover -a low bitumen content, a high percentage ofvolatile matter ranging from 27% to 45 a swelling index according to theASTM D720-46 method of from 2 to 9 and a high oxygen content rangingfrom 6 to 12.5%, such as Saar-Lorraine coals of the types gras A, gras Band ambants gras, which comprises freeing from dust a portion of saidweakly coking coal, crushing said dust-freed portion, separating thecrushed coal into small coal containing gangue and fusain, intomiddle-sized grains containing viirain and clarain and into coarsegrains containing durain, eliminating the small coal for practicallyremoving all of the fusain of said coal, roughly crushing the coarsegrains, mixing the middlesized grains and the roughly crushed coarsegrains, separating the middle-sized granules of the mixture thusobtained, crushing the remaining coarse granule fraction of saidmixture, mixing the crushed coarse granule fraction with themiddle-sized granules of said mixture, preparing a ternary mixturehaving a percentage of volatile matter ranging from 27% to 33% andcomprising as main constituent from 65% to 75% by weight of the granulesobtained yafter said second mixing operation and as secondary componentsfrom 9% to 28% by weight of additional coking bituminous coal having avolatile matter content of 18% to 25 an oxygen content less than 5% andMicum indexes M40 higher than 80 and M10 lower than 8, and from 7% to16% by weight of small grains of a carbonaceous material substantiallyfree of volatile matter, mechanically increasing the bulk density ofsaid ternary mixture, and carbonizing said ternary mixture withincreased bulk density at a temperature comprised between about 1150 C.and 1350 C.

3. A method according to claim 2, wherein the dimensions of the smallcoal range from 0.3 to 2 mm., those of the coarse grains from 10 to 2Omm., while the upper dimensions of the middle-sized grains range from 3to 4 mm.

4. A method according to claim 2, wherein the coarse granules obtainedby the second separation are crushed to granules smaller than 2 mm.

5. A method according to claim 2, wherein the coking bituminous coal isincorporated `in the ternary mixture mixture has a percentage Vofvolatile matter ranging from in granules having a size ib elow4 mm. 29%to 30%.

6. A method according to claim 2.,- wherein the-car- 10. A methodaccording to claim 2, whereinafter the Ibonaceous material substantiallyfree v'from' .volatile matcompression step the bulk density is comprisedbetween ter is incorporated in the ternary mixture inygranules hav- 51,000 and 1,100 llg./m.3.

' di l and t l 17?; :flzrlllaune thluglz mnmpnsmg a least ReferencesCited 1n the le of this patent 7. A method according to claim 2,Awherein the carbo- UNITED STATES PATENTS naceous material substantiallyIfree from volatile matter 1,824,526 Andrews Sept. 22, 1931 1s formed ofcoke breeze. 10 2,091,711 Koppers Aug. 31, 1,937

8. A method according to claim 2, wherein the carbonaceous materialsubstantially free from volatile matter is OTHER REFERENCES formed ofanthracitiecoal culm. Chemical Abstracts: Vol. 44, page V9134, October10,

9. A method according to claim 2*, wherein the ternary 1950, article byPluckman.

1. A METHOD OF PRODUCING METALLURGICAL COKE HAVING MICUM INDEXES M40SUBSTANTIALLY EQUAL TO 80 AND M10 LOWER THAN 8, FROM WEAKLY COKINGCOALS, WHICH COALS HAVE MOREOVER A LOW BITUMEN CONTENT, A HIGHPERCENTAGE OF VOLATILE MATTER RAINGING FROM 27% TO 45*, A SWELLING INDEXACCORDING TO THE ASTM D720-46 METHOD OF FROM 2 TO 9 AND A HIGH OXYGENCONTENT RANGING FROM 6 TO 12.5%, SUCH AS SARR-LORRAINE COALS OF THE TYESCONSISTING OF "GRAS A," "GRAS B" AND "FLAMBANTS GRAS," WHICH COMPRISESFREEING FROM DUST A PORTION OF SAID WEAKLY COKING COAL, CRUSHING SAIDDUST-FREED PORTION, SEPARATING FROM THE CRUSHED COAL SMALL COALCONTAINING FUSAIN AND GANGUE, CRUSHING THE REMAINING PART OF THE CRUSHEDCOAL INTO CENTAGE OF VOLATILE MATTE RANGING FROM 27% TO 33% AND